I was a foundling when my adoptive parents who have no children of their own took me under their care. I was not legally adopted but I am using their last name, because they registered me as their own child. I was given the best education they could provide, and I am now working in a prestigious company here in Dubai.
Two months ago, my adoptive mother passed away but before she died, she gave me all the titles of her pieces of property, which she said she inherited from her parents. My adoptive fathe, however,r does not want me to have a share in the assets.
From your narration of facts, it is apparent that your adoptive parents did not undergo the legal process of adoption, and they resorted to simulation of birth for which they can be held liable under the law. Simulation of birth is defined as the tampering of the civil registry making it appear in the birth records that a certain child was born to a person who is not his/her biological mother, causing such child to lose his/her true identity and status. (Section 3(j), Republic Act No. 8552). Any person who commits an act to make it appear that she gave birth to a child when in truth and in fact she is not the biological mother of the child shall be liable for simulation of birth. Simulation of birth is an act punishable under Article 347 of the Revised Penal Code by prision mayor (six  years and one  day to twelve  years’ imprisonment) and a fine not exceeding one thousand pesos (P1,000.00).
In your case, while it is true that you are using the last name of your adoptive parents in your certificate of live birth, the same, however, was a product of a simulation of birth and not of the legal process of adoption. Your right as an adopted child is dependent on the evidence that you have to show to prove that you have been legally adopted; and, thus entitled to all the rights of a compulsory heir.
Adoption is a juridical act, a proceeding in rem, which creates between two persons a relationship similar to that which results from legitimate paternity and filiation. Only adoptions that have been approved by the courts, or pursuant with the procedure laid down under Rule 99 of the Rules of Court (and under the Family Code, as well as some provisions of the Child and Youth Welfare Code) are valid under our jurisdiction. It is not a natural law at all, but is wholly and entirely artificial. To establish the relation, the statutory requirements must be strictly carried out; otherwise the adoption is an absolute nullity. Also, adoption is never presumed but must be affirmatively proved by the person claiming it (Prof. Jose N. Nolledo, The Family Code Annotated, 2000 Revised Edition, page 331).
The absence of proof of adoption of such order of adoption by the court as provided by statute, cannot be substituted by parol evidence that such a child has lived with a person not his parent, and has been treated as a child to establish such adoption. Even evidence of declaration of a deceased, made in his lifetime, that he intended to adopt a child as his heir, and that he had adopted him, and of the fact that the child resided with the deceased, as a member of his family, from infancy until he attained his age of majority, is not sufficient to establish the fact of adoption (Ibid.).
From the foregoing, the person claiming that he has been adopted must prove the fact of adoption. The best evidence to show proof of adoption is the court order granting the petition for adoption. Also, the birth certificate of the adopted child may also be used to prove the fact of adoption.
We regret to inform you that in the absence of an instrument like that of a last will and testament executed by your deceased adoptive mother instituting you as her heir, you cannot validly question the act of your adoptive father of not allowing you to participate in the assets of your adoptive mother. The ownership of the subject property of your adoptive mother of the pieces of property is of no moment. While it may be true that such assets were exclusively your adoptive mother’s when she was alive, upon her death, your adoptive father was her only compulsory heir. You are not qualified as an heir of your deceased adoptive mother, because you were not legally adopted and such fact is known to you and to your adoptive father. Your adoptive father could always impugn your relationship to him. Any legal action you wish to pursue against your adoptive father will thus be a futile exercise.
It would be different if your adoptive mother left a last will and testament where she instituted you as an heir to her estate. In this instance, you may become an heir of your deceased adoptive mother to the extent of the pieces of property she has left you in her will, regardless if your adoption is legal or not. At any rate, nobody forbids you to try to talk to your adoptive father who, in the past, may have treated you as his daughter. As you said, you were given the best education. That alone is a bounty in itself.
We hope that we were able to answer your queries. Please be reminded that this advice is based solely on the facts you have narrated and our appreciation of the same. Our opinion may vary when other facts are changed or elaborated.
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Editor’s note: Dear PAO is a daily column of the Public Attorney’s Office. Questions for Chief Acosta may be sent to firstname.lastname@example.org